250+ TOP MCQs on Electron Beam Machining – 1 and Answers

Manufacturing Processes Multiple Choice Questions on “Electron Beam Machining – 1”.

1. Mechanism of material removal in Electron Beam Machining is due to _____
a) mechanical erosion due to impact of high of energy electrons
b) chemical etching by the high energy electron
c) sputtering due to high energy electrons
d) melting and vaporisation due to the thermal effect of impingement of high energy electron
Answer: d
Clarification: EBM is typically used with higher power density to machine materials. The mechanism of material removal is primarily by melting and rapid vaporisation due to intense heating by the electrons and laser beam respectively.

2. Electron beam machining is a/an _____ process
a) adiabatic
b) thermal
c) iso-thermal
d) isentropic
Answer: b
Clarification: Electron Beam Machining (EBM) is a thermal process considering the mechanisms of material removal. However electrical energy is used to generate high-energy electrons in case of Electron Beam Machining (EBM).

3. Electron beam machining is carried out in _____
a) high pressure vessel
b) thermally insulated area
c) vacuum
d) in a room at atmospheric pressure
Answer: c
Clarification: Electron Beam Machining is required to be carried out in vacuum. Otherwise, the electrons would interact with the air molecules, thus they would lose their energy and cutting ability.

4. During EBM _____ is kept under vacuum.
a) electron gun
b) whole setup
c) the workpiece
d) laser generation setup
Answer: c
Clarification: The workpiece to be machined is located under the electron beam and is kept under vacuum. The high-energy focused electron beam is made to impinge on the workpiece with a spot size of 10 – 100 μm.

5. As the electrons strike the work material _____
a) heat energy is converted to kinetic energy
b) atomic energy is converted to heat energy
c) kinetic energy is converted to heat energy
d) electrical energy is converted to heat energy
Answer: c
Clarification: The kinetic energy of the high velocity electrons is converted to heat energy as the electrons strike the work material. Due to high power density instant melting and vaporisation starts and “melt – vaporisation” front gradually progresses.

6. The gun in EBM is used in _____ mode.
a) wave guide
b) biasing
c) pulsed
d) high intensity
Answer: c
Clarification: Unlike in Electron Beam Welding, the gun in EBM is used in pulsed mode. Holes can be drilled in thin sheets using a single pulse. For thicker plates, multiple pulses would be required. Electron beam can also be manoeuvred using the electromagnetic deflection coils for drilling holes of any shape.

7. Which of the following is not a function of electron beam gun?
a) generation of electrons
b) accelerating the electrons
c) focusing the beam
d) absorbing the electron beam
Answer: d
Clarification: Electron beam gun is the heart of any electron beam machining facility. The basic functions of any electron beam gun are to generate free electrons at the cathode, accelerate them to a sufficiently high velocity and to focus them over a small spot size. Further, the beam needs to be manoeuvred if required by the gun.

8. ______ is used to make cathode for electron beam gun.
a) Aluminium
b) Rubidium
c) Molybdenum
d) Tantalum
Answer: d
Clarification: The cathode is generally made of tungsten or tantalum. Such cathode filaments are heated, often inductively, to a temperature of around 2500⁰C.

9. Heating to a high temperature leads to thermo-ionic emission.
a) True
b) False
Answer: a
Clarification: In EBM, temperature in the electron beam gun is around 2500⁰C. Such heating leads to thermo-ionic emission of electrons, which is further enhanced by maintaining a very low vacuum within the chamber of the electron beam gun.

10. In the electron beam gun, cathode cartridge is highly negatively biased.
a) True
b) False
Answer: a
Clarification: In the electron beam gun, cathode cartridge is highly negatively biased so that the thermo-ionic electrons are strongly repelled away from the cathode. This cathode is often in the form of a cartridge so that it can be changed very quickly to reduce downtime in case of failure.